Motorola Multicoupler 6 port (opinions)

[mancow]

I got this off ebay a long time ago. It was listed as a 6 port multicoupler. I really haven't used it much due to it having mini uhf connectors. When I did have it hooked up it did seem to work well.

I was thinking about the Stridesberg units and what on earth could make them so expensive. I took this thing apart tonight and was surpised at all the nothing that's in there. The pics tell the story but to elaborate the resistors in the triangle arrangement are 150 ohm. The ones at the end near the connectors are 10 ohm.

I have some panel mount BNCs but of course the bolt pattern is just a hair to big. I am in the process of dremeling the holes toward the center to adapt the BNCs to the existing bolt pattern. My plan is to convert it all over to BNC.

Inside it says Motorola 1988 6 WAY SPLITTER. There is a part number stamped on the side in ink that looks to say BRF4210A.

Does anyone know what this came from? Is it constructed similarly to a Stridesberg model (less the preamp of course)?

What's the theory of operation with the resistor network in there?

 

[MMIC]

Looks like some sort of Wilkinson power divider. Do some internet searches for it - i've conjured up one page here that may explain it a bit (albeit in a very technical sense):

http://www.microwaves101.com/encyclopedia/Wilkinson_splitters.cfm#twoport

I wouldn't know what to tell you as to why it is the size that it is, except that maybe Motorola just wanted to make whomever bought this to begin with for $$$$ feel like they were getting something for their money. Kind of like VCRs these days

 

[rcvmo]

for one thing, the connector at the far end is missing.

there are many useful things for something like this. tie 6 rx to one antenna, but it will be frequency specific, so all rx better be in the band the unit was tuned for.

tie 6 Tx units to one antenna but it will be frequency specific, so all tx better be in the band the unit was tuned for.
I re-confingured one similar that ties 4 X 2.4 ghz rx to one antenna . originally it was in a box simliar to this one, but with SMA connectors. had to play with some caculations and etch the board to make it work in the 2.4 GHz range.
good luck.
rcvmo

 

[mancow]

The connector is missing because I had just removed it to replace it with a BNC.

 

[jim202]

You have what looks like a 6 way power splitter that was used in the
Motorola AMPS cellular equipment. These units were used in the receiver
path to feed multiple receivers off of a common antenna. There were
RF amps that were in line with these receiver power splitters to overcome
the inherit losses.

Remember you don't get anything for nothing. If you take a signal and
split it 6 ways, you end up with a signal at each of the 6 ports that is just
slightly less than 1/6 of the input signal. As such, you always had an
amplifier on the input of these splitters.

You would be better off just obtaining the mini UHF connectors rather
than trying to convert the existing connectors. They are not that expensive
and go on with a simple crimp tool. Most of the current Motorola two
way radios today use these mini UHF connectors.

Jim

 

[iMONITOR]

I was thinking about the Stridesberg units and what on earth could make them so expensive.

People's willingness to pay for them! Don't get me wrong, the Stridesberg units are made well, and work good, but there is no way to justify the price that they charge for these! They have somewhat of a niche in the market and they're milking the ca$h cow!

 

[mancow]

Do they contain anything more than this unit (excluding the preamplified units)? Is there a more elaborate impedance matching system...?

It just made me curious how they compared electrically with something like this. It would be neat to see a picture of the inside of one.

 

[prcguy]

I think MMIC is correct that this is a Wilkenson power divider and probably for the 800MHz band. This type of divider offers low loss and high isolation between ports, but the drawback is their fairly narrow band. Outside the 800MHz region it will degrade and become just a box with wires connecting ports with lossy resistors .
prcguy